1. Field of the Invention
The present invention relates to paint spraying. More specifically, the present invention relates to techniques for monitoring paint conductivity in electrostatic spraying.
While the present invention is described herein with reference to illustrative embodiments for particular applications, it should be understood that the invention is not limited thereto. Those having ordinary skill in the art and access to the teachings provided herein will recognize additional modifications, applications, and embodiments within the scope thereof and additional fields in which the present invention would be of significant utility.
2. Description of the Related Art
Electrostatic spraying is a currently well accepted technique for painting motor vehicles. Electrostatic spraying involves charging a paint bath with one polarity and a target surface with the second polarity. The liquid is then sprayed toward the surface. Paint droplets are electrostatically attracted and bonded to the surfaces of the charged vehicle.
The efficacy of conventional electrostatic spraying systems depends largely on the accurate monitoring of the viscosity of the paint. If the viscosity is too large, the paint coating exhibits lumpiness, a condition commonly referred to as .tbd.orange peel.quadrature.. The conductivity of the paint is a measure of the paint viscosity. Higher conductivity indicates lower viscosity. In addition, the conductivity is related to how well droplets form in the spray nozzle. High conductivity permits better control of droplet size.
Current techniques use electrical equipment to measure the DC (direct current) resistivity of the paint in the bath. This is accomplished by direct contact between electrodes and the paint bath. While this technique may be somewhat effective in measuring the conductivity of the paint in the bath, it is not generally capable of measuring the conductivity of the paint in a spray.
This shortcoming is significant as the electrical properties of the paint have been observed to change with a state change from liquid to spray. Hence, there is a need in the art for a measurement apparatus and technique effective in measuring the electrical properties of paint in a spray form.